modified structure

[avr-crypto-lib.git] / arcfour / arcfour.c

diff --git a/arcfour/arcfour.c b/arcfour/arcfour.c
new file mode 100644 (file)
index 0000000..e07193f
--- /dev/null
+++ b/arcfour/arcfour.c
@@ -0,0 +1,63 @@
+/* arcfour.c */
+/*
+    This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2008  Daniel Otte (daniel.otte@rub.de)
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/*
+ * File:        arcfour.c
+ * Author:      Daniel Otte
+ * email:       daniel.otte@rub.de
+ * Date:        2006-06-07
+ * License:     GPLv3 or later
+ * Description: Implementation of the ARCFOUR (RC4 compatible) stream cipher algorithm.
+ *
+ */
+
+#include <stdint.h>
+#include "arcfour.h"
+
+/*
+ * length is length of key in bytes!
+ */
+
+void arcfour_init(const void *key, uint8_t length_B, arcfour_ctx_t *ctx){
+       uint8_t t;
+       uint16_t x,y=0;
+       for(x=0; x<= 255; ++x)
+               ctx->s[x]=x;
+
+       for(x=0; x<= 255; ++x){
+               y += ctx->s[x] + ((uint8_t*)key)[x % length_B];
+               y &= 0xff;
+               /* ctx->s[y] <--> ctx->s[x] */
+               t = ctx->s[y];
+               ctx->s[y] = ctx->s[x];
+               ctx->s[x] = t;
+       }
+       ctx->i = ctx->j = 0;
+}
+
+uint8_t arcfour_gen(arcfour_ctx_t *ctx){
+       uint8_t t;
+       ctx->i++;
+       ctx->j += ctx->s[ctx->i];
+       /* ctx->s[i] <--> ctx->s[j] */
+       t = ctx->s[ctx->j];
+       ctx->s[ctx->j] = ctx->s[ctx->i];
+       ctx->s[ctx->i] = t;
+       return ctx->s[(ctx->s[ctx->j] + ctx->s[ctx->i]) & 0xff];
+}
+